Stent/fiber structural combinations

ABSTRACT

A plurality of endoluminal segments axially connected by fiber bridges is disclosed. The endoluminal segments may either be balloon-expandable or self-expanding, with the preferred embodiment being superelastic nitinol. The intraluminal segments may possess a textured surface or at least one geometric feature per segment, preferably located at the apex of a strut pair comprising the intraluminal segment, preferably capable of serving as an anchoring point for the fiber bridges. These geometric features may transmit axially compressive loads during deployment from a device such as a catheter, and may further be capable of interlocking the endoluminal segments when constrained within a device such as a catheter. The fibers comprising the bridges may be polymeric, silk, collagen, bioabsorbable, or a blend thereof. The fiber network comprising the bridges may be regularly oriented, randomly oriented, localized, or continuous. Moreover, the intraluminal segments and fiber bridges may be individually impregnated with therapeutic material, or may both be impregnated with therapeutic material.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to axially connected intraluminal segmentsand more particularly to individually expandable segments connected atleast partially by fibers. In addition, the present invention relates tointraluminal devices, and more particularly to intraluminal devices,such as stents, incorporating fibers that operate as bridges axiallyconnecting adjacent stent segments. The present invention also relatesto stent structures having geometric features that serve as fixationpoints for the fibers described herein.

2. Discussion of the Related Art

Intraluminal devices have been known in the art for a number of years.These devices have utilized a variety of materials, but commonly fallinto two broad categories; namely, self-expanding andballoon-expandable. Nickel-titanium is a common material selected foruse in self-expanding device designs, while stainless steel and cobaltalloys have been common materials in balloon-expandable devices.

The flexibility of these devices is an important factor affectingdelivery and performance within the body of the patient. A tortuousvascular anatomy requires a device to be able to conform to theanatomical conditions, before and after deployment, while preserving thedevice's primary functionality. Self-expanding materials providesuperior flexibility relative to balloon-expandable materials for thespecific reason that the self-expanding materials tend to conform to atortuous anatomy with less tissue trauma than balloon-expandablematerials. Examples of self-expanding intraluminal devices includestents, vena cava filters, distal protection devices, and occluders.However, maximizing the flexibility of intraluminal devices may lead tonegative tradeoffs in other aspects of the device's mechanicalperformance, such as radial strength and buckling resistance.Additionally, in many cardiovascular applications, the device may besubject to significant dynamic deformations such as twisting, axialextension/compression and bending not seen in other parts of thevasculature. Under such conditions, a device should preferably be ableto tolerate large dynamic deformations while remaining intact such thatits primary functionality is preserved.

Radially expandable intraluminal devices commonly comprise a pluralityof axially adjacent radially expandable segments. Such axially adjacentradially expandable segments are often joined by connecting elementsgenerally described as bridges. In some cases, these bridge elements arenot radially deformable, but rather are axially deformable, allowing forrelative motion between axially adjacent radially expandable segments.This relative motion may desirably accommodate static or dynamicbending, stretching, or compression of the implanted device. The numberof bridge elements present around the circumference of a design is animportant design consideration. Fewer bridge connections allow for moreflexibility and conformability, but potentially compromise scaffoldinguniformity and vessel coverage. More bridge connections improvescaffolding uniformity, but potentially result in an undesirably stiffstructure.

Radially expandable intraluminal devices are commonly fabricated suchthat the radially expandable segments and bridge elements are integral,or formed from a single continuous material, and therefore the finisheddevice is a single contiguous structure.

The above described loading cases of bending, flexion, stretching, andcompression create design challenges for flexibility and durability ofintraluminal implants. One solution to these design concerns is toprovide a design with fewer integral bridging elements, or ultimately nointegral bridging elements, such that each segment is subject to onlythe localized forces and deformations at its immediate location. Thisdesign presents some difficulty in the precise placement of theindividual segments within the target area of the lumen. Specifically,in the instance of self-expanding materials, the device is introduced ina constrained state within a sheath. As the constraint is removed fromthe self-expanding segment, the rapid increase in diameter createsaxially directed forces which would tend to propel the segment forwardin the absence of adequate axial constraint between the expandingsegment and axially adjacent constrained segment still completely orpartially within the sheath. In circumstances where the segment lengthis somewhat short in comparison to its diameter, this may result in thesegment jumping forward from the distal tip of the delivery device,which in turn creates difficulty in the precise placement of thesegment. Additionally, there is a need to provide a means for ensuringthe uniformity and stability of adjacent segments during deployment.Accurate placement of intraluminal devices is of paramount importance toensure that problems such as inaccurate placement over target lesions,distortion, or occlusion of critical branch vasculature does not occur.

In addition, intraluminal devices are a known means for the delivery oftherapeutic agents to localized areas within the body of the patient. Acommon method for combining the delivery of therapeutic agents into theperformance of an intraluminal device involves coating the surface ofthe device with a polymer containing the therapeutic agent. The surfacearea of the device becomes a limiting factor in the quantity oftherapeutic agents that may be delivered. Coating the device with apolymer may also present difficulty in controlling coating adhesion,controlling coating thickness, and controlling coating interaction withthe therapeutic agent. Consequently, increasing the available surfacearea of the device without sacrificing its mechanical performance andflexibility, or eliminating the need for coating the device surface maysimplify the manufacture and efficacy of such devices.

Accordingly, there exists a need for intraluminal devices that thatavoid the problems described herein.

SUMMARY OF THE INVENTION

The present invention overcomes the disadvantages associated withcurrent intraluminal implant designs as briefly described above.

In accordance with one aspect, the present invention is directed to animplantable intraluminal medical scaffold. The implantable scaffoldcomprises one or more radially expandable stent segments and one or morefiber bridges interconnecting the one or more radially expandablesegments to form a substantially tubular structure.

Radially expandable intraluminal devices are commonly fabricated suchthat the radially expandable segments and bridge elements are integral,or formed from a single continuous material, and therefore the finisheddevice is a single contiguous structure. The present invention isdistinct in that some or all of the bridge elements may be comprised ofa material separate and distinct from the material from which theradially expandable intraluminal device is fabricated. Preferably, theradially expandable intraluminal device structure is fabricated frommetal, while the separate bridging elements are fabricated from anon-metallic polymer material. The present invention also describesmeans for joining the metallic and non-metallic or polymeric elements toprovide a useful device assembly.

In one exemplary embodiment, the present invention is directed to aseries of adjacent intraluminal segments at least partiallyinterconnected with a network of fibers. The fibers supplement orreplace conventional integral bridging elements that are contiguous withradially expandable segments. The fibers preferably allow the individualintraluminal segments to move with some degree of independence fromone-another while providing the benefit of the flexible axial connectionbetween segments. The fibers may be oriented randomly or regularly whilepreferably not inhibiting the expansion of the intraluminal segments toa diameter sufficient to maintain lumen patency and the ability of theintraluminal segments to be constrained to a reduced diameter.

In another exemplary embodiment, the present invention is directedtoward individual intraluminal segments possessing a feature, orfeatures, that provide a means for securing fibers to the individualintraluminal segments. An individual segment may possess one or morefeatures to which the fibers may be attached. The features may be of anygeometry that provides a means for securing fibers. Examples ofcontemplated feature geometries include micro features such as texturedsurfaces, and macro features such as eyelets, tabs, anvils, and thelike. The features may also provide other functionality in combinationwith, or exclusive of, securing the fibers. Additional functionalitiesmay include the interconnection of intraluminal elements prior tocompleted deployment. The fibers may be secured to the feature throughany suitable means such as solvent bonding, looping, knotting,threading, and the like. The fibers may be oriented randomly orregularly while preferably not inhibiting the expansion of theintraluminal segments to a diameter sufficient to maintain lumenpatency. Additionally, the fiber elements may be constructed asindividual filaments, with ordered or random placement, or the fiberelements may be individual strands incorporated into larger fibernetworks such as braids, weaves, threads, and the like. The fibers mayform individual or localized patterns, or may form continuous patterns.The fiber elements may be of any composition suitable for implantationinto the body of a living patient such as polymers, silk, collagen,bioabsorbable materials, and the like. The fibers preferably provide animproved means for accurate implant deployment, implant flexibility, andimplant durability. Moreover, the some or all of the fibers may be usedas a means for delivering therapeutic agents to the patient, either asthe exclusive means, or as an additional means supplementing similarfunctionality, including the intraluminal segments and proceduralmethod. Intraluminal segments may be any self-expanding orballoon-expandable material, or combination of both.

More specifically, the present invention is directed to a stentcomprising adjacent radially expanding stent segments interconnected viaa network of fibers or meshes. The present invention provides increasedtherapeutic versatility to stents of any architecture; further, itprovides a means to enhance the axial stability and uniformity of stentarchitectures having conventional integral metallic bridges connectingaxially adjacent radially expandable segments; further provides for afiber connection of a series of short radially expandable stent segmentswhich are otherwise unconnected. This design also provides forpositioning the stents in an axial series with a predetermined gapbetween each segment.

The present invention provides axial integrity to a series of stents,such that the individual stent segments may not pull apart from eachother when the structure is pulled into axial tension as describedabove.

The present invention provides integrity for a series of stents when ina constrained or expanded configuration. The present invention providesstructural integrity until the stent structure is delivered and deployedin the target vessel. This axial integrity is particularly important atthe moment during which the constrained stent segment emerges from thedelivery system and immediately begins to expand. The force of thisexpansion would tend to propel the individual stent segments forwarduncontrollably without the axial connection provided by the describedfibrous connection.

The axial connection provided by the fiber is not necessarily neededafter the implant has been delivered and deployed. As such, the fibercould be made from a bio-absorbable or dissolving material.

It is expected that the fiber will be combined with the stent structurewhen it is in its expanded configuration (typically 5-10 mm). The fibershould preferably not inhibit radial constraint of the stent from itsexpanded configuration to its low-profile delivery configuration(typically 1-2 mm).

For a device constructed of a self-expanding material such as nitinol,the fiber should preferably not inhibit radial expansion of the stentstructure from its delivery configuration to its memory configurationwhen deployed at the time of implantation.

The nitinol structure may be constrained from its expanded configurationto its delivery configuration under conditions of extreme chilling(typically −10 to −60 degrees C.). Ideally, the fiber material would beable to withstand such chilling, and would maintain its ability to beconstrained in diameter without inhibiting radial constraint of thestent structure.

The memory shape and mechanical characteristics of nitinol areprogrammed using a series carefully controlled thermal exposures atvarious temperatures that are known in the art. Ideally, the completednitinol stent structure should not be exposed to elevated temperatures(greater than 60 degrees C.). Ideally, the fiber material would be ableto withstand such temperatures, and would maintain its ability to beconstrained in diameter without inhibiting radial constraint of thestent structure.

Preferably, the fiber material may also serve as a platform for deliveryof drugs or related therapeutic agents as well as a structural element.

Preferably, the fiber should have proven biocompatibility as animplantable material, and should be commercially available for suchpurposes.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the invention will beapparent from the following, more particular description of preferredembodiments of the invention, as illustrated in the accompanyingdrawings.

FIG. 1 is a schematic view of an exemplary stent-fiber combinationwherein a network of fibers is intertwined with intraluminal segments inaccordance with the present invention.

FIG. 2 is a series of photographs of a preferred embodiment of FIG. 1wherein a textured metallic surface provides improved adhesion betweenthe fibers and metallic substrate.

FIG. 3 is an alternate exemplary embodiment of FIG. 1 wherein fibers areattached to anchoring features on the intraluminal segments inaccordance with the present invention.

FIG. 4 is an enlarged detail view of the exemplary embodimentillustrated in FIG. 3.

FIG. 5 a is a schematic view of the exemplary embodiment illustrated inFIG. 3, wherein the intraluminal segments are at a compressed diameterin accordance with the present invention.

FIG. 5 b is a schematic view of the exemplary embodiment illustrated inFIG. 3 wherein the intraluminal segments are at an expanded diameter inaccordance with the present invention.

FIG. 6 is a detailed view of an alternate exemplary embodiment of thestent-fiber combination illustrated in FIG. 3 in accordance with thepresent invention.

FIG. 7 is a detailed view of an alternate exemplary embodiment of thestent-fiber combination illustrated in FIG. 1 in accordance with thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is directed to a stent comprising individualsegments interconnected by a mesh or fibers. These fibers are integratedwith each other and the radially expandable stent segments in such a waythat provides an axial bridge connection between the stent segmentswithout inhibiting radial expansion or constraint of the stent segments.

FIG. 1 illustrates a plurality of adjacent intraluminal stent segments100 axially connected by a network of fibers 101(x _(n)) where “x_(n)”represents the number of fibers present, ranging from 1 to about 1×10⁹.Each adjacent segment 100 is preferably self-expanding, but may also beballoon-expandable. Adjacent segments may be axially connected byintegral bridging elements 102 as in the group of segments 103, may beaxially independent as in the group of segments 104, or may be acombination of both as in the group of segments 105. Fibers 101 axiallyconnect at least two adjacent segments 100. A preferred exemplaryembodiment is a self-expanding intraluminal segment 100 made from asuperelastic alloy such as nickel-titanium (nitinol) comprising fromabout 50.0 weight percent Ni to about 60 weight percent Ni, with theremainder being Ti. Preferably, each intraluminal segment 100 isdesigned such that it is superelastic at body temperature, having anaustenitic finish temperature in the range from about twenty-two degreesCelsius to about thirty-seven degrees Celsius. Fibers 101(x _(n)) aremost preferably polymers, silk, collagen, or bioabsorbable compositions.In FIG. 1, fibers 101(x _(n)) may be of one, or more than one materialcomposition, including embodiments where single fibers 101(x _(n)), orgroups of fibers 101(x _(n)) are composed of differing materialsrelative to the other fibers 101(x _(n)) forming an interwoven network.Fibers 101(x _(n)) may be oriented randomly, or in a regular pattern,such that the fibers 101(x _(n)) preferably allow the intraluminalsegments 100 to move relative to one another while axially connectedthrough the network of fibers 101(x _(n)). One preferable means forallowing relative movement is illustrated in FIG. 7, where fibers 701(x_(n)) are looped over one another while being passed over and under thestruts forming the individual intraluminal segments 700.

FIG. 2 illustrates a preferred embodiment of a textured surface designedto optimize the adhesion of polymer fibers to a metallic radiallyexpandable intraluminal implant. This highly magnified view illustratesa metallic coating 201 with a textured surface 202 deposited on asubstrate 200. The textured surface 202 provides increased surface areato improve bonding of polymeric fibers 203. In a preferred embodiment,the metallic coating 201 provides a biocompatible surface and issecurely bound to the base metallic structure 200 using a physical vapordeposition process. In a preferred embodiment, metallic coating 201 istantalum and the substrate 200 is a radially expandable metallic nitinolsegment. Tantalum has the benefits of enhancing radiopacity, as well apreserving biocompatibility of the device. The polymer fibers 203 arejoined to metallic surface 202 with the aid of a solvent which allows atleast some of the dissolved polymer to form an interface between thetextured surface and fiber.

In accordance with another exemplary embodiment, FIG. 3 and FIG. 4illustrate a plurality of intraluminal segments 300 connected by aplurality of fibers 302(x _(n)), where “x_(n)” represents the number offibers present, ranging from 1 to about 1×10⁹. The intraluminal segments300, and fibers 302(x _(n)) are substantially as described in FIG. 1,where intraluminal segment 300 has at least one additional geometricfeature 305 preferably located at the apex of an individual strut paircomprising the intraluminal segment 300 structure. The geometric feature305 serves as an attachment point between fibers 302(x _(n)) andintraluminal segments 300. The geometric feature 305 or notched tab mayfurther serve to provide a means for transmitting axially compressiveloads between intraluminal segments 300 during deployment within thetarget lumen. In addition, the geometric feature 305 may comprise amaterial that is more radiopaque than the remaining portions of thestructure, thereby serving as a marker for accurate deployment of thedevice. As illustrated in FIG. 3 and FIG. 4, one preferred means forattaching the fiber 302(x _(n)) to the geometric feature 305 of theintraluminal segment 300 is to create a knotted loop 304. The fibers302(x _(n)) that form a network connecting intraluminal segments 300 maybe of a single material composition such as those mentioned as beingpreferable in FIG. 1, or may be of more than one preferable material.

FIG. 5 a and FIG. 5 b are schematic representations of the exemplaryembodiment illustrated in FIG. 3 and FIG. 4 and described herein. FIG. 4a shows a plurality of intraluminal segments 300, having geometricfeatures 305 and connected fibers 302(x _(n)) that are radiallycompressed in a manner generally consistent with being constrainedwithin a catheter. FIG. 5 b shows the same plurality of intraluminalsegments 300, geometric features 305, and connected fibers 302(x _(n))and 304 as in FIG. 5 a, however, the intraluminal segments 300 are inthe fully-expanded state.

In accordance with another alternate exemplary embodiment, intraluminalsegments 100 connected by a network of fibers 101(x _(n)) as shown inFIG. 1, or a network of fibers 302(x _(n)) as shown in FIG. 3 throughFIG. 5 b, are a means for delivering therapeutic agents to the patient.A detailed description of exemplary agents is included herein. Thefibers 301(x _(n)) or 302(x _(n)) may either be the exclusive means ofdelivery, or may provide surface area in addition to that of theintraluminal segments 100, 300. Fibers 101(x _(n)) or 302(x _(n)) aremost preferably impregnated with therapeutic agents, or combinations oftherapeutic agents, such as those that inhibit the formation ofthrombus, or the reoccurrence of stenosis. The fibers 101(x _(n)) or302(x _(n)) that form a network connecting intraluminal segments 100,300 may be of a single material composition such as those mentioned asbeing preferable in FIG. 1, or may be of more than one preferablematerial thereby creating a blended fiber.

In accordance with yet another exemplary embodiment, FIG. 6 illustratesthe detail of a geometric feature 606 similar to the feature 305 shownin FIG. 3 and FIG. 4. In this exemplary embodiment, the geometricfeature 606 is substantially similar to that of 305 in that it serves asan anchoring point for a fiber 607, or fibers 607, as well as providinga means for transmitting axially compressive forces between intraluminalsegments 600 during deployment to the target lumen. In this exemplaryembodiment, the fiber 607 is passed through the eyelet preferably formedby the geometric feature 606, where the fiber 607 terminates in amanner, such as a knot that preferably restrains the terminus of thefiber 607 from falling out of the geometric feature 606. The means bywhich fibers 607 are secured to the plurality of intraluminal segments600 may either be through knotting the fiber 607 at its terminationpoints on the first (proximal) and last (distal) intraluminal segments600, or at intervals between intraluminal segments 600 along the lengthof the fiber 607. The geometric feature 606 is preferably located at theapex formed by adjacent struts comprising intraluminal segment 600,where there is preferably at least one feature 606 on each intraluminalsegment 600 present. The fibers 607 that form a network connectingintraluminal segments 600 may be of a single material composition suchas those mentioned as being preferable in FIG. 1, or may be of more thanone preferable material. The number of fibers 607 present may range from1 to about 1×10⁹. Optionally, the fibers 607 may either be the exclusivemeans, or may provide surface area in addition to that of theintraluminal segments 600, for the delivery of therapeutic agents.Fibers 607 are most preferably impregnated with therapeutic agents, orcombinations of therapeutic agents, such as those that inhibit theformation of thrombus, or the reoccurrence of stenosis.

It is important to note that the fibers may incorporate any suitablebiocompatible materials that may be non-absorbable or absorbabledepending upon the application.

As set forth above, the stent segments, the fibers or both may be usedto deliver therapeutic and pharmaceutic agents including:anti-proliferative/antimitotic agents including natural products such asvinca alkaloids (i.e. vinblastine, vincristine, and vinorelbine),paclitaxel, epidipodophyllotoxins (i.e. etoposide, teniposide),antibiotics (dactinomycin (actinomycin D) daunorubicin, doxorubicin andidarubicin), anthracyclines, mitoxantrone, bleomycins, plicamycin(mithramycin) and mitomycin, enzymes (L-asparaginase which systemicallymetabolizes L-asparagine and deprives cells which do not have thecapacity to synthesize their own asparagines); antiplatelet agents suchas G(GP) ll_(b)/lll_(a) inhibitors and vitronectin receptor antagonists;anti-proliferative/antimitotic alkylating agents such as nitrogenmustards (mechlorethamine, cyclophosphamide and analogs, melphalan,chlorambucil), ethylenimines and methylmelamines (hexamethylmelamine andthiotepa), alkyl sulfonates-busulfan, nirtosoureas (carmustine (BCNU)and analogs, streptozocin), trazenes—dacarbazinine (DTIC);anti-proliferative/antimitotic antimetabolites such as folic acidanalogs (methotrexate), pyrimidine analogs (fluorouracil, floxuridineand cytarabine) purine analogs and related inhibitors (mercaptopurine,thioguanine, pentostatin and 2-chlorodeoxyadenosine {cladribine});platinum coordination complexes (cisplatin, carboplatin), procarbazine,hydroxyurea, mitotane, aminoglutethimide; hormones (i.e. estrogen);anti-coagulants (heparin, synthetic heparin salts and other inhibitorsof thrombin); fibrinolytic agents (such as tissue plasminogen activator,streptokinase and urokinase), aspirin, dipyridamole, ticlopidine,clopidogrel, abciximab; antimigratory; antisecretory (breveldin);anti-inflammatory; such as adrenocortical steroids (cortisol, cortisone,fludrocortisone, prednisone, prednisolone, 6α-methylprednisolone,triamcinolone, betamethasone, and dexamethasone), non-steroidal agents(salicylic acid derivatives i.e. aspirin; para-aminophenol derivativesi.e. acetaminophen; indole and indene acetic acids (indomethacin,sulindac, and etodalec), heteroaryl acetic acids (tolmetin, diclofenac,and ketorolac), arylpropionic acids (ibuprofen and derivatives),anthranilic acids (mefenamic acid, and meclofenamic acid), enolic acids(piroxicam, tenoxicam, phenylbutazone, and oxyphenthatrazone),nabumetone, gold compounds (auranofin, aurothioglucose, gold sodiumthiomalate); immunosuppressives: (cyclosporine, tacrolimus (FK-506),sirolimus (rapamycin), azathioprine, mycophenolate mofetil); angiogenicagents: vascular endothelial growth factor (VEGF), fibroblast growthfactor (FGF); angiotensin receptor blockers; nitric oxide donors,antisense oligionucleotides and combinations thereof, cell cycleinhibitors, mTOR inhibitors, and growth factor receptor signaltransduction kinase inhibitors; retenoids; cyclin/CDK inhibitors; HMGco-enzyme reductase inhibitors (statins); and protease inhibitors.

In accordance with another exemplary embodiment, the stents describedherein, whether constructed from metals or polymers, may be utilized astherapeutic agent or drug delivery devices. The metallic stents may becoated with a biostable or bioabsorbable polymer or combinations thereofwith the therapeutic agents incorporated therein. Typical materialproperties for coatings include flexibility, ductility, tackiness,durability, adhesion and cohesion. Biostable and bioabsorbable polymersthat exhibit these desired properties include methacrylates,polyurethanes, silicones, polyvinylacetates, polyvinyalcohol,ethylenevinylalcohol, polyvinylidene fluoride, poly-lactic acid,poly-glycolic acid, polycaprolactone, polytrimethylene carbonate,polydioxanone, polyorthoester, polyanhydrides, polyphosphoester,polyaminoacids as well as their copolymers and blends thereof.

In addition to the incorporation of therapeutic agents, the coatings mayalso include other additives such as radiopaque constituents, chemicalstabilizers for both the coating and/or the therapeutic agent,radioactive agents, tracing agents such as radioisotopes such as tritium(i.e. heavy water) and ferromagnetic particles, and mechanical modifierssuch as ceramic microspheres. Alternatively, entrapped gaps may becreated between the surface of the device and the coating and/or withinthe coating itself. Examples of these gaps include air as well as othergases and the absence of matter (i.e. vacuum environment). Theseentrapped gaps may be created utilizing any number of known techniquessuch as the injection of microencapsulated gaseous matter.

In a preferred embodiment, the fiber elements are formed using acontinuous fiber spinning process. In this process polymer is dissolvedwith solvent in a highly viscous solution. The solution is dispensedthrough a nozzle or spinneret to form a polymer fiber. This fiber iscollected by a spinning mandrel on which the stent segments arepositioned. The mandrel rotates and indexes back and forth axially tocover the stent segments with polymer fiber. When the polymer fibercontacts the surface of the stent segments, it preferentially stillcontains enough solvent to allow for adequate solvent bonding of thefibers to each other and the surface of the metallic substrate. Thisprocess provides fibers typically in the 10 micron to 100 microndiameter range.

In another preferred embodiment, the fiber elements are formed using anelectrospinning process. Herein, the polymer is typically dissolved in asolvent solution and dispensed from a spinneret and directed toward atarget. A high voltage potential between the spinneret and target, inthe range of 1 kV to 50 kV, creates electrostatic forces that attractthe solution toward the target. Between the spinneret and mandrel, thestream of polymer in solution is transformed to a fine fiber as most ofthe solvent evaporates. The target is typically a rotating metallicmandrel that is either grounded or charged. Stent segments arepositioned on this rotating mandrel and covered with polymer fibersusing this electrostatic forming process. The mandrel may rotate atvarious speeds, and also index back and forth axially or spin around acarousel to achieve preferential alignment of the fibers in the axial orcircumferential directions. This electrostatic spinning processtypically produces fibers in a range less than one micron in diameter.

The density of the fibers may be allowed to vary from a relativelysparse network to a relatively dense network. As density increases, thedevice approaches the configuration of a stent graft, and may provide abarrier to flow or fluid penetration. Such an implementation with adense mesh of biostable fibers approaches the form and function of astent graft. However, with a dense mesh of bioabsorbable or dissolvingfibers provides the functionality of a temporary stent graft; such adevice may have utility in a variety of clinical circumstances,including acute repair of a vascular perforation. In a preferredembodiment, the fibers are arranged in a relatively sparse network, suchthat the fibers to do not provide a complete barrier to flow or fluidpenetration. Such a sparse architecture is especially preferred in caseswhere the implanted device crosses branch vessels where it is desirableto maintain patency of such branch vessels.

Although shown and described is what is believed to be the mostpractical and preferred embodiments, it is apparent that departures fromspecific designs and methods described and shown will suggest themselvesto those skilled in the art and may be used without departing from thespirit and scope of the invention. The present invention is notrestricted to the particular constructions described and illustrated,but should be constructed to cohere with all modifications that may fallwithin the scope for the appended claims.

1. An implantable intraluminal medical scaffold comprising: one or moreradially expandable stent segments; and one or more flexible fiberbridges interconnecting the one or more radially expandable stentsegments to form a substantially tubular structure.
 2. The implantableintraluminal medical scaffold according to claim 1, wherein the one ormore radially expandable stent segments comprise a balloon-expandablematerial.
 3. The implantable intraluminal medical scaffold according toclaim 2, wherein the balloon-expandable material comprises stainlesssteel.
 4. The implantable intraluminal medical scaffold according toclaim 2, wherein the balloon-expandable material comprises acobalt-chromium alloy.
 5. The implantable intraluminal medical scaffoldaccording to claim 1, wherein the one or more radially expandable stentsegments comprise a self-expanding material.
 6. The implantableintraluminal medical scaffold according to claim 5, wherein theself-expanding material comprise a nickel-tilonium alloy.
 7. Theimplantable intraluminal medical scaffold according to claim 1, whereinthe one or more flexible fiber bridges comprise individual filaments. 8.The implantable intraluminal medical scaffold according to claim 1,wherein the one or more flexible fiber bridges comprise fiber networks.9. The implantable intraluminal medical scaffold according to claim 1,wherein the flexible fiber bridges comprise polymeric materials.
 10. Theimplantable intraluminal medical scaffold according to claim 1, whereinthe flexible fiber bridges comprise silk.
 11. The implantableintraluminal medical scaffold according to claim 1, wherein the flexiblefiber bridges comprise collagen.
 12. The implantable intraluminalmedical scaffold according to claim 1, wherein the flexible fiber bridescomprises bioabsorbable materials.
 13. The implantable intraluminalmedical scaffold according to claim 1, wherein the flexible fiberbridges comprise non-bioabsorbable materials.
 14. The implantableintraluminal medical scaffold according to claim 1, wherein the one ormore radially expandable stent segments comprise a textured surface. 15.The implantable intraluminal medical scaffold according to claim 1,wherein at least one of the one or more radially expandable stentsegments and the one or more flexible fiber bridges comprise atherapeutic agent affixed thereto.
 16. The implantable intraluminalmedical scaffold according to claim 1, wherein at least one of the oneor more radially expandable stent segments and the one or more flexiblefiber bridges comprise a therapeutic agent incorporated therein.
 17. Theimplantable intraluminal medical scaffold according to claim 1, whereinthe one or more flexible fiber bridges form an interwoven network. 18.The implantable intraluminal medical scaffold according to claim 1,further comprising attachment elements.
 19. The implantable intraluminalmedical scaffold according to claim 18, wherein the attachment elementsare affixed to one or more of the one or more radially expandable stentsegments.
 20. The implantable intraluminal medical scaffold according toclaim 19, wherein one or more of the one or more flexible fiber bridgesare connected to the attachment elements.